Elevator system for mine shaft

ABSTRACT

An underground elevator system for mine personnel comprised of support mast formed from a plurality of prefabricated structural sections that are connected in an end-to-end arrangement and secured to one side of an excavated shaft. The mast includes an emergency escape ladder enclosed by removable wire mesh and a cab movable along and guided by one side of the mast, the cab being mounted thereon by means that can be adjusted to maintain it level despite the degree of mast incline. The cab is driven by cable hoist means mounted at the top of the mast and includes an overspeed-catching means and a slip-sensing safety means.

United States Patent 1111 3,627,079

[72] Inventors Swend F. L. Nielsen 3,178,048 4/1965 Bergman 187/12 SanMateo; 3,204,721 9/1965 Park 1. 182/178 Guido K. Wegner, Paclllce, bothof Calif. 3,298,462 1/1967 Morris 182/178 [21] Appl. No. 872,8983.5l7,775 6/1970 Meyer 187/95 1 Filed Oct-31.1969 FORElGN PATENTS 2; T m2 7 C I 1,443,262 6/1966 France 187/6 1 1 1 974,317 11/1960 Germany187/12 1,294,078 4/1969 Germany 1. 254/173 Primary Examiner- Harvey C.Hornsby [54] ELEVATOR SYSTEM FOR MINE SHAFT Almmey-Owen, Wickersham &Erickson 9 Claims, 23 Drawing Figs.

An under ground elevator system for mine per- 187/20 187/27 187/94187/95 182/178 sonnel comprised of support mast formed from a pluralityof I 254/173 prefabricated structural sections that are connected in anend- {251 112150;6515;:3113311111111::iijjijijij: "1: 1231 10792, andside of shaft. The mast includes an emergency escape ladder enclosed951254/173; 182/178 by removable wire mesh and a cab movable along andguided [56] References Cited by one side of the mast, the cab beingmounted thereon by means that can be adjusted to maintain it leveldespite the UNITED STATES PATENTS degree of mast incline. The cab isdriven by cable hoist means Pratt mounted at the top of the mast andingludes an ove speed- 1,891 81181111611 catching means and aslip..sensing afety mean5 2,232,890 2/1941 Stillwagon 187/12 2,463,2153/1949 Strachan 187/95 5 T: is its 28 s s 25 k 5 is 2 e 42 5 9 k; 0 3 s1 a i s ,9 if P 1 i s Patented Dec. 14, 1971 3,627,079

6 Sheets-Sheet 1 FIG 4 Patented Dec. 14, 1971 3,627,079

6 Sheets-Sheet 2 q u 14 64a 6 FIG- 5 INVENTORS F| 7 swam) F. L. NIELSENBY GUIDO K. WEGNER ATTORNEYS Patented Dec. 14, 1971 3,627,079

6 Sheets-Sheet 3 FIGJO 42 FIG 9 H FIG I sws flo F' L l z l l eu GUIDO K.w GNER ATTORN EYs' Patented Dec. 14, 1971 31%;? 7 W? 6 Sheets-Sheet 5HNVENTORS SWEND F. L. NNELSEN M1 BY sumo K. WEGNER F fl ATTORNEYSPatented Dec. 14, 1971 3,627,07

6 Sheets-Sheet 6 POWER CONTROL CIRCUIT I |9o I82 .1) I84 Q I72 I70 I III I [I I64 I66 :1 i I I l 3 I I I58 I I62 I I60 Q I56 FIG-J9 FIG-20SWEND F.L. NIELSEN BY sumo K. WEGNER ATTORNEYS ELEVATOR SYSTEM FOR MINESHAFT This invention relates to an improved elevator or verticaltransportation system for installation in underground mine shafts anddie like.

Timber beam construction has long been used for mine shafts and the liketo provide the means to reinforce the shaft and support an elevator cageand its counterweight. Generally, such construction comprised a doublecompartment arrangement as required by mine safety standards, with onecompartment housing the elevator or cage and the other compartmentincluding provisions for an escape ladder in the event of a powerfailure. Such timber type construction had several disadvantages andcreated certain problems, because it was complicated, expensive and timeconsuming to install, as well as being vulnerable to fire and the otherlimitations inherent with wood. A general object of the presentinvention is to overcome these disadvantages while solving the problemof providing a mine hoist system having the required safety facilities.

Another object of the present invention is to provide a mine hoistsystem that can be erected quickly and easily with a minimum requirementfor labor and equipment and, more particularly, one that canbeprefabricated in sections and then assembled later within a shaft withthe sections fixed to the walls of the shaft. The invention alsoprovides a system wherein the mast sections themselves as well as otherequipment for the hoisting system can be easily dismantled and movedelsewhere or modified and increased in size.

Still another object of the present invention is to provide a mine hoistsystem utilizing prefabricated metal mast sections in a mine shafthaving strong, structural connector means capable of being anchoredfirmly in irregular shaft walls. The aforesaid connector meanscompensate for irregular surfaces of the shaft walls and therebymaintain longitudinal alignment of the mast or tower sections withsufficient accuracy to enable them to serve as guide rails for avertically movable cage frame and a cab attached thereto.

Most underground mine shafts penetrate the ground at an angle close to avertical line, but this angle may vary over a considerable range fordifferent shafts. Since the mast within the shaft necessarily isoriented at the same angle as the shaft and the cab is movable on andguided by the mast, some means must be provided for attaching the cab tothe mast so that the cab floor will be level. Another object of thepresent invention is to provide an adjustable connection between the caband the mast that will allow the cab to assume a normal position as itmoves up and down.

Yet another object of the present invention is to provide a slip sensingmeans on the cable drive system for the cab that will automaticallyarrest the cab if any slippage occurs when the cab is supposed to bestopped at any point on the mast.

The aforesaid and other objects are accomplished by a prefabricatedtower or mast comprised of interconnectable sections that can be loweredinto an underground shaft and then fastened together and also to a wallof the shaft to form a supporting structure for a movable cab. Eachsection in addition to providing the required structural strengthincludes an internal ladder and protective walls. When connected, themast sections provide a complete, protected escape means from any levelof the shaft. Structural members of the sections form rails to which aremovably attached a cage frame that supports a personnel cab or freightplatform. The cage frame is controlled by cables connected to a hoistingmechanism at the top of the mast and to a counterweight located at oneside of the mast. The cab is operable by conventional controls through acontrol cable extending from the cab to the hoist mechanism at the upperend of the mast. The mast is easily installed and set up for operationand when necessary, it can be dismantled and moved to another locationwith a relatively small expenditure of time and labor.

Other objects, advantages and features of the present invention willbecome apparent from the following detailed description which ispresented with the accompanying drawing, in which:

FIG. 1 is a view in front elevation showing an assembled mine shafthoist system embodying the principles of the present invention;

FIG. 2 is a view in side elevation of the mine hoist system shown inFIG. 1;

FIG. 3 is an enlarged fragmentary view in perspective showing the powerdrive system at the upper end of the hoist system;

FIG. d is an enlarged fragmentary view in elevation showing the lowerend of the mine hoist system according to the present invention;

FIG. 5 is a view in side elevation of one mast section for the minehoist system shown in FIGS. I and 2;

FIG. 6 is a view in front elevation of the mast section shown in FIG.11;

FIG. 7 is a top view of the mast section shown in FIG. 5;

FIG. 8 is an enlarged fragmentary plan view showing one comer of a mastsection;

FIG. 9 is a view in front elevation of the cage frame for the mine hoistsystem according to the present invention;

FIG. I0 is a view in side elevation and in section taken along the line10-40 of FIG. 9;

FIG. 11 is an enlarged fragmentary view in section taken along the lineIll-ll of FIG. 9;

FIG. Ila is a view in section taken along the line Ilia-41: of FIG. Ill;

FIG. 12 is an enlarged fragmentary view in section taken along the line12-12 of FIG. 9;

FIG. 12a is a view in section taken along the line l2a-l2a of FIG. 12;

FIG. 13 is an enlarged view in section taken along the line 13-13 ofFIG. 9;

FIG. 13a is a view in section taken along the line Ilia-13a of FIG. 13;

FIG. 141 is a greatly enlarged view in side elevation showing a portionof a mast section with the cab attached thereto;

FIG. 15 is a further enlarged fragmentary view in elevation showing oneconnection of the cab on the cage frame;

FIG. 16 is an enlarged plan view showing the connectors for securing themast sections to a shaft wall;

FIG. 17 is a view along line I7-l7 ofFIG. 16;

FIG. 18 is a view in elevation and in section taken along line I8-ll8 ofFIG. 17;

FIG. I9 is an enlarged view in side elevation showing the slip sensingdevice on the power control section;

FIG. 20 is a view in front elevation and partially in section of thedevice shown in FIG. 19.

GENERAL DESCRIPTION Referring to the drawing, FIG. 1 and 2 :show a minehoist assembly 20 embodying the principles of the present invention asit appears when installed in a typical mine shaft 22 that extendsdownwardly from a surface opening and interconnects mine drifts 241 atvarious levels. The mine shaft may be formed by any conventionalexcavation method and has generally a rectangular cross section. Asshown, the shaft enters the ground at an angle to the vertical, as iscommon in shaft mining, but the present mine hoist is adaptable forinstallation in shafts inclined as much as 40 to the horizontal.Generally, the mine hoist assembly comprises a plurality ofprefabricated mast or tower sections 26 that interconnect together in anend-to-end arrangement and are fixed by anchoring means 28 to one wallof the shaft. The upper mast section 26a forms a support platform 30 fora power drive unit which, as shown in FIG. 3, includes an electric motor32 connected through a suitable transmission and control unit 34 to awinch or traction sheave 36 to which a series of lifting cables 38 areattached. The lower mast section 26b is supported at the bottom of theshaft in a body of concrete 40, unless the surrounding rock material issufficiently stable to serve the same purpose. The intermediate mastsections 26 between the top and bottom sections 26a and 26b are allstructurally identical and are interconnected to form the complete toweror mast of the desired height. 7

Connected to and movable up and down the mast is a cage frame 42 towhich are attached the lifting cables 38 from one side of the tractionsheave 36. As shown in FIG. 2, the same cables from the other side ofthe traction sheave extend down the shaft and are connected to the upperend of a counterweight 44. For hoists over 300 feet high, a series ofcompensating ropes 46 are fixed to the lower end of the counterweight 44and extend downwardly and around a series of compensating rope sheaves48 supported in the base mast section 2612, as shown in FIG. 4. From thelatter sheaves these compensating ropes extend upwardly and are fixed tothe lower end of the cage frame.

Attached to the cage frame 42 is a cab 50 for carrying personnel whichis adjustable in its position so that it can remain level despite theslope or incline of the mast sections 26. The cab contains operatingcontrols which preferably are similar to those in automatic passengerelevators thereby making the hoist operable by any personnel andeliminating the need for a special hoist operator. Details of suchcontrol systems are available in the prior art and will not be describedherein since they do not comprise part of the present invention. Acontrol cable 52 from the cab controls extends through a control cabletrolley 54 that is movably supported in a trolley rail 56 fixed adjacentto one side of the connect mast sections 26. This trolley rail extendsfrom approximately the midheight of the mast to near its base. From thetrolley the control cable extends upwardly to the power drive unit.Thus, as the cab moves up and down on the mast, the control cable iskept straight and under tension and thus free from entanglement withsurrounding structure.

THE MAST SECTIONS 26 As shown in FIGS. -7, each mast section 26 iscomprised of pairs of upright front and rear structural members 58 and60 which are parallel, spaced apart and connected by suitable cross beammembers 62 and 63 at their upper and lower ends. Preferably theseupright members have a square tubular cross section and at their upperand lower ends each has a transverse plate 64 or 64a. The plates 64 atthe top ends are each provided with a diagonal slot 66 while the plates64a at their bottom ends have similarly oriented vertical aligner plates68 which are fixed so that they extend below the ends of the uprightmembers. Thus, when one mast section 26 is placed on top of anothersection the aligner plates 68 at the lower ends of the upper section fitwithin the slots 66 of the lower section and maintain the two connectedsections 26 and their upright members in perfect alignment. The crossbeam members 62 at the upper and lower ends of each section, as shown inFIG. 8, have horizontal flange portions 70 that are flush with thetransverse end plates 64 and 64a of the upright members. These flangeportions have bolt holes 72 at predetermined lo cations near their endswhich automatically align and match with similar holes on adjoiningsections when the guide plates 68 are inserted within the slots 66 asdescribed. Bolts (not shown) through these holes 72 are then easilyinserted and tightened to hold the adjoining mast sections firmlytogether.

Additional diagonal reinforcing members 74 are used to interconnect theupright members 58 and 60 and strengthen each mast section. Extendingfrom the lower end to the top end of each section, preferably at aslight angle to the vertical, is a ladder 76. On the sides of each mastsection between the two front'upright members and between the front andrear upright members on both sides are panels 78 of a suitable wire meshmaterial such as expanded metal mesh. This provides a protective shieldaround the mast for anyone using the emergency ladder. The wire meshpanels are secured by suitable fasteners and are thus easily removableso that access to the ladder can be readily accomplished at any pointalong the mast.

As shown in the cross-sectional view of FIG. 8, the front uprightmembers 58 of each mast section 26 are larger in cross section than therear upright members 60 and they extend outwardly from the sides of theinterconnecting frame members 62 and 63. Thus, on each front uprightmember there are front and rear parallel surfaces 80 and 82 and a planarouter side surface 84, all of which extend its full length. These threesurfaces thus provide guide means forretaining the cage frame 42 on themast as it moves up and down.

THE MAST-ANCHORING SYSTEM The mast sections are attached to one wall ofthe shaft by means of rockbolts 136. While various types of rockboltsmay be used depending on the nature of the material surrounding theshaft, a preferred structural arrangement for anchoring the mastsections using rockbolts is shown in FIGS. 16 to 18. Generally, itcomprises a structural cross beam 138 having a box type cross section towhich are attached a pair of retaining plates 140. The latter arehook-shaped'in plan form and fit around the rear upright members 60 of amast section 26, the upright members fitting into the pockets 142 of theretainer plates 140. Spaced outwardly from the retaining plates on thebeam are openings 144 through which the rockbolts extend. When the mastis erected, the rockbolts 136 are first set in drilled holes in theshaft wall at the proper spacing. The beam 138 is then placed inposition with the retaining plates hooked around the mast members 60 andthe rockbolts extending through openings 144 in the beam. Timber blocksand wedges 146 are placed between the beam 136 and the shaft wall 148 totake up excess space. Anchor nuts 150 which bear against channel-shapedwasher plates 152 are attached to the end of each rockbolt. With themast and beam adjusted to the proper position using the shims 146 wherenecessary, the anchor nuts are then tightened to secure the mastsections to the shaft wall.

THE CAGE FRAME 42 The cage frame 42, as shown in FIGS. 9 to 13, isfabricated from structural steel members in a conventional manner andcomprises essentially a pair of parallel, spaced apart side members 86interconnected by suitable supporting cross members 88. Spaceddownwardly from the top end of each side member is an upper connector 90for holding the cage frame on a front mast member 58. As shown in FIGS.11 and 11a, these upper connectors are comprised of a pair of front andside rollers 92 and 94 which are rotatably mounted on the cage frame sothat their axes are at right angles to each other and their surfaceswill engage the front and side surfaces 80 and 84 of a front mast member58. A pair of third or rear rollers 96 which are narrower than the frontroller 92, are spaced from it so as to engage the rear surface 82 of thefront mast member. Each upper connector thus surrounds a front mastmember on three sides and thereby holds the cage frame on the mast.Spaced upwardly from the lower end of the cage frame are a pair of lowerconnectors 98 as shown in detail in FIGS. 12 and 124. Each of theselower connectors comprises a pair of rollers 100 and 102 which aremounted on the cage frame with their axes at right angles to each other,thereby positioning the rollers so that they engage the front and sidesurfaces 80 and 84 of the front mast members 58. Another pair of rollers104 as shown in FIGS. 13 and 13a are preferably mounted on a bottomcross beam 106 at the lower end of the cage frame 42 and are positionedto engage the front surface of the front mast members. The cross beam106 is attached to but spaced from a similar cross beam 108 and mountedtransversely between these two beams are five pins or bolts 110 to whichthe ends of the compensating ropes 46 are attached. Fixed to theopposite ends of the cross beams 108 and 110 are a pair of circularplates 112 that serve as contact pads for engaging a pair of bumpersprings 114. The latter springs are mounted at the bottom end of themast section as shown in FIG. 4.

THE CAB 50 The cab is essentially a fabricated steel frame 116 mountedon a platform 118 to which walls 120 of sheet metal and/or heavy wiremesh material are attached. The walls are held in place by any suitablefasteners that allow them to be easily removable when desired. Both avertical sliding door on one side and horizontal swinging doors on theother side may be provided as well as an escape hatch in the ceiling onthe cab. in accordance with an important feature of the invention thecab is attached to the cage frame 42 by means of removable pins and alinkage that allows the cab to remain level despite an angle of inclineon the mast. As shown in FIGS. 14 and 15, the cab frame 116 isreinforced at one end of a bottom frame member 11% by a plate 126 whichis bored to receive a lower pin 12%. A corresponding bottom frame memberon the other side of the cab is similarly bored to receive another lowerpin. These two lower pins 128 are axially aligned and extend throughsimilarly aligned bore holes located near the lower end of the outerlongitudinal members 86 of the cage frame. At the top of the cab are apair of top frame members 130 that are provided with axially alignedbores for receiving a pair of pins (not shown) each of which alsoextends through one end of a link 132. The other ends of both of theselinks are connected by a pair of pins 134 that extend through alignedbores near the upper end of the cage frame. The holes near opposite endsof the links 132 are spaced apart so that the cab will assume a normallylevel position when the links are attached to the cage frame. Fordifferent angles of the shaft and thus the mast installed therein, thedistance between the holes for the pivot pins in the links 132 can bevaried so that the cab will be level. Links with a series of alternateholes can be provided to provide for cab level adjustment.

THE SLIP-SENSING DEVICE 154 As part of the power drive and controlsystem a slip-sensing means 154 is provided on the upper mast section260 which detects any slippage of the lifting cables 38 on the tractionsheave 36. As shown in FIGS; 19 and 20, this device is mounted on aplatfonn 156 adjacent to the traction wheel and comprises an arm 158which is pivotally connected at its lower end to a bracket 160 fixed tothe platform. Extending upwardly from the bracket and in line with thearm is a stationary member 1162 to which is fixed a bolt 164 thatextends horizontally through the arms. A coil spring 166 surrounds thebolt with one end of the spring being retained by a nut I68 on the endof the bolt. The opposite end of the spring bears against the arm,thereby urging it in one direction toward the traction wheel. At theupper end of the pivotal arm is a bracket 170 supporting a pin 172 towhich is pivotally connected a pair of links 1174. At theirlower endsthe links rotatably support a shaft 176 to which is attached a lowercontact roller 178, and at their upper ends these links 174 supportanother shaft 180 to which is fixed an upper roller 182. The upperroller normally turns with its shaft when it is free to do so, but ifthe roller is restrained while the shaft 180 is turned, the roller 182will tend to move axially on the shaft. The lower roller 178 ispositioned to bear directly against one lifting cable 38 extending fromthe traction wheel while the upper roller 182 is positioned to engagethe traction wheel itself. Both of the shafts 176 and 1180 are providedwith small sprocket wheels 184 which are connected by a small continuouschain 186 so that the rotation of the two rollers is normally .the same,as when there is no slippage of the cable on the traction wheel. Theupper roller has an annular groove 188 near one end within which ridesthe arm 190 of a limit switch 192. The latter, which may be any suitabletype that is commercially available, is connected in the power controlcircuit of the hoist drive.

The operation of theslip sensing cutoff device should be apparent fromthe foregoing description. lf slippage of the lifting cable 38contacting the lower roller 178 occurs, the lower roller willrotatefaster than the upper roller 182. Since the.

two roller shafts 176 and 1180 are connected by a direct chain drive 186the upper shaft 180 will be driven by the lower roller 178 and its shaft176 and thus the upper shaft will rotate faster than the upper roller.This causes the upper roller M2 to move axially on its shaft and therebyactuates the limit switch arm 190 that rides in the groove of the upperroller.

As stated previously the control system for the cab or elevator may beof any suitable type that is commercially available. In addition, thesystem may include the usual safety provisions such as a suitableoverspeed'catching device. From the foregoing it should be apparent thatthe present invention provides a unique mine hoist that may be erectedwith a minimum of labor in a relatively short time. The only on siteconstruction jobs are the assembly of the mast sections and theirattachment to a shaft wall. Yet, the system has the versatility andsafety features of much more complicated and expensive permanent mineelevator installations.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intendedto be inany sense limiting.

We claim:

ll. A combined elevator and escape passage for installing in .a mineshaft comprising:

a plurality of prefabricated mast sections each having parallel spacedapart front and rear longitudinal members connected by crossmembers;

means on the ends of said longitudinal members for connecting said mastsections together in longitudinal alignment;

means for securing said rear longitudinal members to one wall of themine shaft;

cage frame means movably mounted on said front longitudinal members; I

a cab extending outwardly from said. cage frame and means for adjustablyconnecting said cab to said cage frame for keeping it in a levelposition for varied angular positions of the mast sections;

each mast section including a ladder located within the cross-sectionalarea defined by said longitudinal members, and wall means attached tosaid longitudinal members to provide a protected escape passage; and

power control means mounted on a top mast section including liftingcables connected to said cage frame means for moving it up and down onsaid connected front longitudinal members of said mast sections.

2. The elevator system as described in claim 1 wherein said frontlongitudinal members on each mast section have a flat sided crosssection, aligner means fixed in the ends of said longitudinal membersfor maintaining the longitudinal members of adjoining mast sections inalignment.

3. The elevator system as described in claim ll wherein means forconnecting said mast sections together includes aligner means comprisingtransverse plates fixed to the ends of said longitudinal members, anedge mounted plate fixed to each said transverse plate at one end ofeach mast section, and slots in said plates located at the other end ofsaid mast section; and bolt means through said cross members ofadjoining mast sections adjacent said longitudinal members.

4. The elevator system as described in claim I wherein said adjustablemeans comprises a pair of fixed pivotal connections between the lowerend of said cab and the cage frame and a pair of links each pivotallyconnected at one end to said cage frame and at the other end to theupper end of said cab.

5. The elevator system as described in claim 11 wherein said means forsecuring said rear longitudinal] members to the shaft wall comprises atransverse beam, hook: means on said beam for engaging said rearlongitudinal members, a pair of spaced apart rock bolts adapted to beembedded in the shaft wall, and means for securing the ends of said rockbolts to said transverse beam.

6. The elevator system as described in claim 1 wherein said powercontrol means on said upper mast section includes a traction wheel,motor means and means drivingly connecting said motor means to saidtraction wheel, a counterweight, cable means extending around saidtraction wheel and connected at opposite ends to said cage frame and tosaid counterweight.

7. The elevator system as described in claim 6 wherein slipsensing meansadjacent said power control means for sensing any relative slippage ofcables on said traction wheel,

8. The elevator system as described in claim 7 wherein said slip-sensingmeans comprises means contacting said traction wheel and a cable thereonand responsive to a differential movement between them for deactivatingsaid power control means.

9. An elevator system for installation in a mine shaft comprising:

a plurality of prefabricated mast sections each having parallel spacedapart front and rear longitudinal members connected by cross members;

means on the ends of said longitudinal members for connecting said mastsections together in longitudinal alignment;

means for securing said rear longitudinal members to one wall ofthe mineshaft;

cage frame means movably mounted on said front longitudinal members;

a cab attached to said cage means;

power control means mounted on a top mast section including a tractionwheel, motor means and means drivingly connecting said motor means tosaid traction wheel, a counterweight and lifting cables extending aroundsaid traction wheel and connected at opposite ends to said cage frameand to said counterweight for moving the cage frame up and down on saidconnected front longitudinal members of said mast sections;

and slip-sensing means adjacent said power control means for sensing anyrelative slippage of cables on said traction wheel, said slip-sensingmeans comprising a pair of first and second rollers mounted on a pair ofspaced apart first and second shafts, respectively, means for supportingsaid shafts so that said first roller engages said traction wheel andsaid second roller engages a cable that extends around said tractionwheel, chain means drivingly connecting said shafts, means on said firstshaft for causing axial movement of said first roller whenever its rateof rotation is less than that of said shaft, and means on said firstroller for actuating a switch to stop said power control means when saidfirst roller is caused to move axially.

lOlOH 0l60

1. A combined elevator and escape passage for installing in a mine shaftcomprising: a plurality of prefabricated mast sections each havingparallel spaced apart front and rear longitudinal members connected bycrossmembers; means on the ends of said longitudinal members forconnecting said mast sections together in longitudinal alignment; meansfor securing said rear longitudinal members to one wall of the mineshaft; cage frame means movably mounted on said front longitudinalmembers; a cab extending outwardly from said cage frame and means foradjustably connecting said cab to said cage frame for keeping it in alevel position for varied angular positions of the mast sections; eachmast section including a ladder located within the crosssectional areadefined bY said longitudinal members, and wall means attached to saidlongitudinal members to provide a protected escape passage; and powercontrol means mounted on a top mast section including lifting cablesconnected to said cage frame means for moving it up and down on saidconnected front longitudinal members of said mast sections.
 2. Theelevator system as described in claim 1 wherein said front longitudinalmembers on each mast section have a flat sided cross section, alignermeans fixed in the ends of said longitudinal members for maintaining thelongitudinal members of adjoining mast sections in alignment.
 3. Theelevator system as described in claim 1 wherein means for connectingsaid mast sections together includes aligner means comprising transverseplates fixed to the ends of said longitudinal members, an edge mountedplate fixed to each said transverse plate at one end of each mastsection, and slots in said plates located at the other end of said mastsection; and bolt means through said cross members of adjoining mastsections adjacent said longitudinal members.
 4. The elevator system asdescribed in claim 1 wherein said adjustable means comprises a pair offixed pivotal connections between the lower end of said cab and the cageframe and a pair of links each pivotally connected at one end to saidcage frame and at the other end to the upper end of said cab.
 5. Theelevator system as described in claim 1 wherein said means for securingsaid rear longitudinal members to the shaft wall comprises a transversebeam, hook means on said beam for engaging said rear longitudinalmembers, a pair of spaced apart rock bolts adapted to be embedded in theshaft wall, and means for securing the ends of said rock bolts to saidtransverse beam.
 6. The elevator system as described in claim 1 whereinsaid power control means on said upper mast section includes a tractionwheel, motor means and means drivingly connecting said motor means tosaid traction wheel, a counterweight, cable means extending around saidtraction wheel and connected at opposite ends to said cage frame and tosaid counterweight.
 7. The elevator system as described in claim 6wherein slip-sensing means adjacent said power control means for sensingany relative slippage of cables on said traction wheel.
 8. The elevatorsystem as described in claim 7 wherein said slip-sensing means comprisesmeans contacting said traction wheel and a cable thereon and responsiveto a differential movement between them for deactivating said powercontrol means.
 9. An elevator system for installation in a mine shaftcomprising: a plurality of prefabricated mast sections each havingparallel spaced apart front and rear longitudinal members connected bycross members; means on the ends of said longitudinal members forconnecting said mast sections together in longitudinal alignment; meansfor securing said rear longitudinal members to one wall of the mineshaft; cage frame means movably mounted on said front longitudinalmembers; a cab attached to said cage means; power control means mountedon a top mast section including a traction wheel, motor means and meansdrivingly connecting said motor means to said traction wheel, acounterweight and lifting cables extending around said traction wheeland connected at opposite ends to said cage frame and to saidcounterweight for moving the cage frame up and down on said connectedfront longitudinal members of said mast sections; and slip-sensing meansadjacent said power control means for sensing any relative slippage ofcables on said traction wheel, said slip-sensing means comprising a pairof first and second rollers mounted on a pair of spaced apart first andsecond shafts, respectively, means for supporting said shafts so thatsaid first roller engages said traction wheel and said second rollerengages a cable that extends around said traction wheel, chain meansdrivingly connecting said shafts, means on said first shaft for causingaxial movement of said first roller whenever its rate of rotation isless than that of said shaft, and means on said first roller foractuating a switch to stop said power control means when said firstroller is caused to move axially.